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الجمعة، 4 أكتوبر 2013

Questions raised over Iraq congenital birth defects study

The
release of a study on congenital birth defects in Iraq has been met
with controversy, with some experts questioning its methodology and peer
review. Paul C Webster reports.

Children who were born with birth defects in Fallujah (pictured November, 2009)

WHO officials have stepped in to defend an unsigned and sharply criticised report
released by the Iraqi Ministry of Health (MOH) on congenital birth
defects in areas where US-led coalition forces used toxin-laced
munitions.

Although several recent studies from Iraq reported worrying rates of
congenital birth defects in areas where highly toxic munitions such as
depleted uranium shells were used by British, US, and other coalition
forces, the new study, which was cofunded by the Iraqi Government and
WHO, found “no clear evidence to suggest an unusually high rate of
congenital birth defects in Iraq”. After initially referring questions
about the study to Iraqi officials, Jaffar Hussain, WHO's Head of
Mission in Iraq, told the The Lancet last week that the report is
based on survey techniques that are “renowned worldwide” and on the
work of international experts who peer reviewed the data “extensively”.

The study, which is based on a 2012 survey of mothers in 10 800
households from 18 Iraqi districts, relies largely on mothers' memories
of the details of spontaneous abortions, stillbirths, and births with
congenital defects since the 1980s (43 387 pregnancies). Citing a lack
of medical records for older events, the Iraqi Government interviewers
were able to view medical files for only 32% of the total reported
cases.

Although warning that the surveyed mothers' recollections might not be
accurate, the report does note a three-fold increase in reported birth
defects between 1988—92 (7·6 per 1000 births) and 2003—07 (26·2 per 1000
births). Nonetheless, it asserts “the rates for spontaneous abortion,
stillbirths and congenital birth defects found in the study are
consistent with or even lower than international estimates”. The
reported stillbirth rate for 2008—12 is considerably lower than
WHO-established norms, the study indicates, leading it to suggest
“possible underreporting of stillbirths, or that stillbirth rates in
Iraq are lower than estimated elsewhere”.

WHO says that since the issue of associating birth defects “with
exposure to depleted uranium has not been included in the scope of this
particular study, establishing a link between the [congenital birth
defects] prevalence and exposure to depleted uranium would require
further research”. According to Jaffar, “there is still further room for
more detailed analysis” and WHO is discussing producing a more detailed
report with the Iraqi MOH.

The study notes that WHO offered technical services to the Ministry,
and that WHO convened an “expert peer review meeting” on the study in
late July with six experts from the London School of Hygiene and
Tropical Medicine (LSHTM), University College London (UCL), the US
Centers for Disease Control and Prevention (CDC), and the Norway-based
Fafo Research Foundation. WHO says this meeting was organised after “it
was determined the work should also undergo the scientific standard of
peer review”.

That may not have been fully achieved, however. Simon Cousens,
professor of epidemiology and statistics at LSHTM, who was among those
invited by WHO to review the study, says he “attended a relatively brief
meeting of around one and a half hours, so just gave some comments on
an early presentation of the results. I wouldn't classify that as
thorough peer review.”

At the CDC in Atlanta, Georgia, spokeswoman Belsie Gonzalez confirmed
that CDC officials “did participate in the peer review meeting at the
invitation of the WHO Regional Office for the Eastern Mediterranean. CDC
did not participate in any aspects of the study. We provided data
interpretation advice on the report.”

Several of WHO's expert reviewers raise methodological concerns about
the study. Its “main limitation is that it is largely based on what
people reported, without any medical examination”, says Cousens. At the
Fafo Foundation in Oslo, social anthropologist John Pedersen adds that
the study's limited geographical scope (Iraq has more than 100
districts) sharply reduces its relevance in understanding the national
pattern and prevalence of birth defects in Iraq. “I wouldn't necessarily
have designed the study in the same way as it was designed”, explains
Pedersen, who notes that lower rates of birth defects could be expected
from mothers' recollections than if doctors had been asked to report
them.

“I agree with Jon Pedersen that there are limitations in the study
design”, says Bernadette Modell, emeritus professor of community
genetics at UCL. “However, it is really difficult to conduct
epidemiological studies of congenital disorders outside a high-income
setting, because many congenital disorders are difficult to diagnose
without sophisticated clinical and laboratory facilities and a
relatively high proportion of those that occur in lower-income settings
may be due to environmental causes.”

Taking these limitations into account, Modell adds, “I think the Iraq
study was pretty good, and as objective as was feasible. I was
particularly impressed with the efficient organisation of
data-collection when the study was underway. The reviewers all agreed
that the data provide no evidence to support claims of an epidemic of
congenital anomalies either nationally, or in any particular area.
However, the study amassed a very large amount of data, which needs
further analysis, ideally with expert assistance.”

Keith Baverstock, author of a 2004 UN report that highlighted the
potential seriousness of Iraq's legacy of intensive exposure to depleted
uranium ordinance employed by British and American troops both during
the First Gulf War of 1991, and after the US-led occupation in 2003,
says the report's reliance on the term “peer review” does not conform
with conventional usage. “It's really misleading”, he charges. “I have
to question what the role of WHO is in this study as a whole”,
Baverstock adds after noting that the study names no authors from WHO or
the Iraqi MOH although a WHO website does explain it did provide
“technical assistance on study design, methodology, data collection,
data analysis and report writing”. For his part, WHO's Jaffar confirms
that “the ownership of study and the authorship of the report is with
the MOH from the outset”.

Researchers in Iraq, the UK, and the USA who have probed congenital
birth defects and have published recent peer-reviewed studies also
express concerns about the methodology employed by the Iraqi MOH and
WHO.

Although WHO says that “at this point no effort to neither substantiate
nor negate the findings of other studies can be employed because the
study is not aiming to establish cause-effect associations between
[congenital birth defects] prevalence and environmental risk factors”,
the study issued by the Iraqi Government states that “in recent years
there have been several anecdotal reports of geographical regions with
an unusually high prevalence of congenital birth defects in Iraq. Most
of the reports did not meet the norms for an objective study of birth
defects, and a review of the published literature could find no clear
evidence to support their findings.”

Samira Alaani, a paediatrician in Fallujah, Iraq, who copublished a 2011 study
utilising hospital records to conclude that congenital malformations
accounted for 15% of all births in Fallujah since 2003, says the new
study cofunded by WHO and the Iraqi Government should have employed
hospital records more comprehensively.

Muhsin Al-Sabbak of the Basrah Medical School in Basrah, Iraq, who copublished a 2012 study
reporting a 17-fold increase in birth defects in the Al Basrah
Maternity Hospital since 1994, warns that the data from Basrah in the
new study does not match local hospital records.

Alison Alborz is a specialist on learning disabilities in children at the University of Manchester, UK, who published a 2013 study
presenting data from a 2010 survey of 6032 households in four Iraqi
governates including data for more than 10 000 children and young people
showing a prevalence of congenital birth defects more than 2·5 times
higher than reported in the Iraqi Government study. She says the new
report gives little information about sampling and does not offer any
discussion of whether the districts chosen for analysis “reflect the
characteristics of the governorate as a whole”.

Mozhgan Savabieasfahani, a toxicologist based in Michigan, USA, who
coauthored the Alaani and Al-Sabbak studies, agrees with Alborz that the
selection criteria determined by the MOH are not sufficiently
explained. “Based on information available in this report, we cannot
rule out selection bias issues”, she warns. She also questions the
decision not to employ hospital records more comprehensively, and notes
that the report suffers from a lack of detail regarding “which areas
were exposed to bombardment or heavy fighting and which areas were not.
The exposed and unexposed populations remain unidentified throughout.”

Tariq Al-Hadithi of the Hawler Medical University in Erbil, Iraq, who
undertook the literature review cited by the Iraqi Government in
describing the work of Alaani, Al Sabbak, Alborz, and Savabieasfahani as
not meeting objective norms, reached a conclusion that was far more
tentative than the Iraqi Government suggests. “As not enough data on
pre-1991 Gulf War prevalence of birth defects are available”, Al-Hadithi
stresses, “the ranges of birth defects reported in the reviewed studies
from Iraq most probably do not provide a clear indication of a possible
environmental exposure including [depleted uranium] or other
teratogenic agents.”